This invention relates to a process for purification of crude argon.
By "crude argon" is meant a mixture, which contains about 90 to 99% by volume of argon and small amounts of oxygen and nitrogen. Such a mixture accumulates at the head of a crude argon column, which is connected to a unit for the low-temperature separation of air. To recover pure argon (about 99.999%) from crude argon, the crude argon must be purified, for example, by rectification in a pure argon column.
In a process of this type, which is known from DE-OS 34 28 968 (FIG. 2), the crude argon is removed in liquid form from the head of the crude argon column. To prevent operating troubles in the crude argon column, a part of the crude argon in the head of the column is removed in gaseous form and recycled to the air separation unit. The crude argon removed in liquid form undergoes an increase in pressure by virtue of its hydrostatic head and is then evaporated. After the addition of hydrogen, the oxygen contained in the crude argon is reacted therewith, and the resulting H.sub.2 O is removed in a drier. The remaining gas mixture is cooled and finally is passed into the pure argon column.
Such a process, on the one hand, is advantageous since the pressure increase of the crude argon requires no additional machinery, but on the other hand, it is economically unsatisfactory because a part of the recovered crude argon is recycled to the air separation unit, whereby separation work already performed is lost in the process.